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Subject[REVERT for 3.1-rc7] staging: zcache: revert "fix crash on high memory swap"
Hi Greg --

Please revert the following commit, hopefully before 3.1 is released.
Although it fixes a crash in 32-bit systems with high memory,
the fix apparently *causes* crashes on 64-bit systems. Not sure why
my testing didn't catch it before but it has now been observed in
the wild in 3.1-rc4 and I can reproduce it now fairly easily.
3.1-rc3 works fine, 3.1-rc4 fails, and 3.1-rc3 plus only this
commit fails. Let's revert it before 3.1 and Seth and Nitin and I
will sort out a better fix later.

Reported-by: Francis Moreau <francis.moro@gmail.com>
Reproduced-by: Dan Magenheimer <dan.magenheimer@oracle.com>

Thanks,
Dan

commit c5f5c4db393837ebb2ae47bf061d70e498f48f8c
Author: Seth Jennings <sjenning@linux.vnet.ibm.com>
Date: Wed Aug 10 12:56:49 2011 -0500

staging: zcache: fix crash on high memory swap

zcache_put_page() was modified to pass page_address(page) instead of the
actual page structure. In combination with the function signature changes
to tmem_put() and zcache_pampd_create(), zcache_pampd_create() tries to
(re)derive the page structure from the virtual address. However, if the
original page is a high memory page (or any unmapped page), this
virt_to_page() fails because the page_address() in zcache_put_page()
returned NULL.

This patch changes zcache_put_page() and zcache_get_page() to pass
the page structure instead of the page's virtual address, which
may or may not exist.

Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Acked-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
index 855a5bb..a3f5162 100644
--- a/drivers/staging/zcache/zcache-main.c
+++ b/drivers/staging/zcache/zcache-main.c
@@ -1158,7 +1158,7 @@ static void *zcache_pampd_create(char *data, size_t size, bool raw, int eph,
size_t clen;
int ret;
unsigned long count;
- struct page *page = virt_to_page(data);
+ struct page *page = (struct page *)(data);
struct zcache_client *cli = pool->client;
uint16_t client_id = get_client_id_from_client(cli);
unsigned long zv_mean_zsize;
@@ -1227,7 +1227,7 @@ static int zcache_pampd_get_data(char *data, size_t *bufsize, bool raw,
int ret = 0;

BUG_ON(is_ephemeral(pool));
- zv_decompress(virt_to_page(data), pampd);
+ zv_decompress((struct page *)(data), pampd);
return ret;
}

@@ -1539,7 +1539,7 @@ static int zcache_put_page(int cli_id, int pool_id, struct tmem_oid *oidp,
goto out;
if (!zcache_freeze && zcache_do_preload(pool) == 0) {
/* preload does preempt_disable on success */
- ret = tmem_put(pool, oidp, index, page_address(page),
+ ret = tmem_put(pool, oidp, index, (char *)(page),
PAGE_SIZE, 0, is_ephemeral(pool));
if (ret < 0) {
if (is_ephemeral(pool))
@@ -1572,7 +1572,7 @@ static int zcache_get_page(int cli_id, int pool_id, struct tmem_oid *oidp,
pool = zcache_get_pool_by_id(cli_id, pool_id);
if (likely(pool != NULL)) {
if (atomic_read(&pool->obj_count) > 0)
- ret = tmem_get(pool, oidp, index, page_address(page),
+ ret = tmem_get(pool, oidp, index, (char *)(page),
&size, 0, is_ephemeral(pool));
zcache_put_pool(pool);
}

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